1. Field of the Invention
The present invention relates to a semiconductor device, and more particularly, to a capacitor and a method for fabricating the same, which can simplify a fabrication process and reduce parasitic capacitances between signal lines, which improves a device reliability.
2. Background of the Related Art
In general, there are the stack type and the trench type in the capacitors, and in turn there are the fin type and the cylinder type in the stack type. In order to secure a capacitance effectively, in general cylinder type of capacitors are used in 64MDRAM. However, in a case of 256MDRAM which is involved in a severe dimensional reduction, it is a general trend that an HSG (Hemi-Spherical Grain) is applied to a related art structure of the 256MDRAM for increasing a capacitance capacity.
A related art method for fabricating a capacitor will be explained with reference to the attached drawings. FIGS. 1A.about.1G illustrate sections showing the steps of a related art method for fabricating a capacitor.
Referring to FIG. 1A, a first insulating layer 12 is formed on a semiconductor substrate 11 having a cell transistor formed thereon, and bitlines 13 are formed on the first insulating layer 12, selectively. A second insulating layer 14 is formed on the first insulating layer 12 inclusive of the bitline 13, planarized, and a silicon nitride film 15 is formed on the second insulating layer 14. A third insulating layer 16 is formed on the silicon nitride film 15, and a first photoresist 17 is coated on the third insulating layer 16, and subjected to patterning by exposure and development, to define a storage node contact region. As shown in FIG. 1B, the patterned first photoresist 17 is used as a mask in etching the third insulating layer 16, the silicon nitride film 15, the second insulating layer 14, and the first insulating layer 12 selectively, to form a storage node contact hole 18 which exposes a surface of the substrate 11 As shown in FIG. 1C, after the first photoresist 17 is removed, an insulating sidewall 19 is formed on an inside surface of the storage node contact hole 18. Then, a conductive material, such as polysilicon, for storage node contact is deposited on the third insulating layer 16 inclusive of the substrate, and planarized until the third insulating layer is exposed, to form a storage node contact 18a which is a conductive material stuffed in the storage node contact hole 18. As shown in FIG. 1D, a conductive material 20 for a capacitor lower electrode is formed on the third insulating layer 16 inclusive of the storage node contact 18a. And, a second photoresist 17a is coated on the conductive material 20 for capacitor lower electrode, and subjected to patterning by exposure and development, to define a capacitor lower electrode region. As shown in FIG. 1E, the patterned second photoresist 17a is used as a mask in etching the conductive material 20 for capacitor lower electrode selectively to remove the conductive material selectively, to form a capacitor lower electrode 20a electrically connected to the storage node contact 18a. As shown in FIG. 1F, the third insulating layer 16 is removed by wet etching to expose the silicon nitride film 15. And, a capacitor dielectric film 21 is deposited on the capacitor lower electrode 20a inclusive of the silicon nitride film 15. Then, as shown in FIG. 1G, upon formation of a capacitor upper electrode 22 on the capacitor dielectric film 21, the related art method for fabricating a capacitor is completed.
In the meantime, in the related art, if a ferroelectric film is used as a capacitor dielectric film, in order to prevent oxidization of the polysilicon of the storage node contact due to a strong oxidizing atmosphere, formation of an oxidization prevention film on the capacitor node contact is required.
However, the related art method for fabricating a capacitor has the following problems.
First, the parasitic capacitance between the storage node contact and the bitline taking place inevitably for devices 256MDRAM class and over with very small sized device affects a device reliability, greately.
Second, in formation of a cylinder type capacitor, if a surface is extended down to a bottom surface of a capacitor lower electrode, a coupling parasitic capacitance is occurred between the capacitor upper electrode and the bitline with a dielectric film inbetween.
Third, if the capacitor dielectric film is formed of a ferroelectric material, formation an additional oxidizing prevention film is required for preventing the polysilicon of the storage node contact from being oxidized by the strong oxidizing atmosphere, resulting in a complicated fabrication process.